Arun and I always discuss about the ways of marketing products and services and making them sell. Especially when we were working on an eMarketing project, we had done some extensive research on how to sell things on the net.
One of the good examples i got then was of 37 Signals and since then i'm closely watching them and learning lessons about application building as well as selling them online.
I came across this blog post recently at Signal Vs Noise (37 Signals official Blog) where they explain how do they do PR, Marketing & Advertising for their products. Its all the same - A very interesting post.